Separation of the bearing cap from the body of the rod by fracture has been known for several years. More particularly, prior U.S. Pat. No. 6,536,642 describes an automated apparatus for implementing the separation of the bearing cap from the body of a connecting rod, with subsequent remating and screwing of the union bolts. Such apparatus is suitable both for rods having an orthogonal cracking plane and for rods having a cracking plane that is askew to the body of the rod. With reference to the apparatus described in the above patent, the big end of the connecting rod, which is to be cracked, is engaged by two crescents that are operable to radially move away from each other by a piston, which is sealingly slidable within a radial chamber made in one of the crescents, and is driven by a hydraulic cylinder via a hydraulic pressure multiplier.
The above device, having a hydraulically operated piston, allows the connecting rods to be cracked with satisfactory accuracy and repeatability, in a way that minimizes deformation of the workpiece caused by yield stress. However, the biasing action of the piston in said prior document is applied to the connecting rod in a way that is partially asymmetrical so that, also in consideration of the unavoidable wear over time, the above, known apparatus is frequently subjected to malfunctions and requires replacements.